1. Field of the Invention
This invention relates generally to interface apparatus for monitoring a plurality of analog input signals and for applying corresponding digitized signals to a digital system bus and, more particularly, to apparatus and method for providing electrooptical isolation of the analog input signals from the digital system bus. The invention also provides circuitry for enabling the analog input signals to be scanned in any desired order. In addition, a gain setting for each analog input is programmable.
2. Description of the Related Art
It is known in the related art to provide an interface unit to process analog input signals and to apply a digitized version of the analog input signals to a digital system bus.
However, the known prior art systems have been so constructed that the digital system bus has been physically coupled to the analog input channels, and this has often given rise to detrimental performance.
Moreover, known prior art systems have required that the gain setting for the analog input channels be set by manual adjustment of variable potentiometer, strap option, or the like, with the result that such gain adjustment has generally been time-consuming and inflexible.
In addition, prior art systems have lacked any mechanism for quickly and reliably setting the order in which a plurality of analog input channels will be read by the interface system.
There has therefore existed an urgent need for an interface between analog input signals and a digital data processing unit system bus that permits the analog input channels to be electrically isolated from the digital system bus and associated host data processing system. There has also existed an urgent need for an interface unit in which the gain for each analog input channel and the order in which such channels are read can be quickly adjusted.